Greetings from Dallas!

Welcome, You should feed him fresh veges everyday (It helps if you make a feeding timetable! I have one if you would like to see). And you should also feed him 1/8 or 1/4 a cup a day of pellets,You can either feed half in the morning and half in the evening or all in the morning or all in the evening, though it would probably be better to do half in the morning and half in the evening. He should also have good hay available to him 24/7. Guinea Pigs also need extra Vitamen C in their deit (Veges are a great way to give it to them) because they do not store their own.

He should always have water.
Yes a 2x3 c&c cage is big enough for one, I found it not enough space to let my girl run around in so upgraded it to a 2x4 +2x1 L shape and she loves it heaps! If you have more space then I would say give him a bigger cage ( It is what he will spend most of his life in!) or if you don't then a 2x3 is the minimum size for one or two piggies.

Piggies are social animals and are happier in groups, are you thinking about adopting a friend for him sometime in the near-ish future? You can get another boy to go with him, I have 3 boars living together in harmony.

Would he be unhappy without another piggy?
Also what veggies are best to give them. Thanks again

Also as far as placement does it scare them if they are on floor? Or should the cage be more waist level?

If you have lots of time to spend on him, so he doesn't get lonely then no he won't get unhappy but it is really best to get him a buddy. How old is he?
Red or green leaf lettuce and bell peppers should the staples in the diet. It's better if you can split that into two or three feedings.
See https://www.guineapigcages.com/forum/...ants-list.html for what you can feed and how often.

The lady at the store said 3.5-4 years
I can hold him and he is fine; but when I put him back in his cage he is very scared

At that age I would say if you were to get him a friend get a young guinea pig.
If you just got him today then I'm not surprised. Guinea pigs are naturally prey animals so it will take a while (usually takes 1 week - months) for him to trust you and not to be scared.
My new girl associates her name with fresh veges so will come to me every time I say her name, maybe to get him use to you could do something like that.

Where can I get a young guinea pig? Also should I increase the cage size?
What is an appropriate price for a young one also. Thanks ^^

I just gave him some strawberries ^^ I saw those on that list you linked!

I'm not sure where you live, see I live in New Zealand and there are no guinea pig rescues in the whole country. But I would search around a see if there is a resuce near you, I would say to try and look for a guinea pig to adopt that is around 2 years old? I'm not quite sure but my big boys were 1 and a half years old when I introduced my new little 5 week old boy them and they get along great.

Haha, that's great just make sure you don't give him to much, as I only feed my pigs strawberries once every two weeks.

Any chance of seeing some pigtures of your guy? Whats his name?

When I get a second one how do I introduce them? Do they have to be separate at first?

First of all, you will need to quarantine the new pig in a separate room away from your current one; for around 3 weeks.

After the three weeks is over and you are sure he's healthy, introduce all of them in a neutral area where none of the pigs have been to.

If they get along, move them into a thoroughly cleaned cage together.

See these links.
Guinea Pigs Social Life
https://www.guinealynx.info/forums/viewtopic.php?t=46468

Read though this link:
https://www.guinealynx.info/healthycavy.html

TONS of great information there.

Read this: https://www.guinealynx.info/quarantine.html
You MUST do this or run a risk of getting your first one sick.

Finally here is information on introductions:

Guinea Pigs Social Life

Hope this helps.

Ok thanks guys!

So if after three weeks the new one does not seem sick then it is ok to put them together?
Should I put them both into a smaller cage for three weeks then introduce them to main cage after three weeks if they seem well.

Yes, after 3 weeks if there is no sign of sickness then it is fine to introduce them to each other.
What I would do would be to keep your pig in his 2x3, either make a 2x3 for the other piggy or keep him in a pet store cage if you have one (just for the three weeks). Then while you introduce them in a play pen or something, make a bigger c&c for both of them to go into after a couple of hours in the play pen.

Thats just what I would do. Remember to keep the cages in different rooms.