Old cars use R12, you can't buy that without a license.
Newer cars use R134a, you can get that at WalMart.
Honda switched over in early '90s, my '95 is R134a. There will be a sticker in the engine compartment saying which it is.

You need pressure gauges for either type, & the correct pressures are different.

If your expansion valve or receiver/dryer is plugged, and you just add a can of refrigerant, you could really hose up your AC. So make sure you know what you're doing.