When you say you want to paint it, do you mean you want it painted or you will be painting it. Are you painting the entire vehicle or just the top?
There is a world of difference between the options above. If you have the equipment to paint and a facility that can be turned into a temporary paint booth and the know how to do it, you already know how to find the paint. So I am guessing this is a first for you.
On the door or jam there is or there was a sticker that provided you the color codes used on the vehicle. Those codes are what paint suppliers use to mix the paint. If the sticker is missing web sites like this can help you find the codes
http://duplicolor.com/
There are probably a half dozen paint manufactures in the US. All provide a paint system for their products. The "system" is the various coatings needed to go from bare metal to shiny top coat. The types of coatings available changes from state to state depending on their regulations. For instance in CA you can't use solvent based paints when re-spraying a vehicle. It must be waterborn (except for the clear coat, no one has developed a water based clear coat, yet).
For professionals and even DIYers, places like
http://wescopbe.com/ provide body preparation supplies, equipment, paint and at some locations even training. This company is only on the west coast. There are suppliers like them all over the country.
If you are going to do it yourself and have no experience, all I can say is, Youtube is you best friend.