I have a SMC Pentax-M 50mm 1:2 prime lens and a Pentax MC auto 28mm 1:2.8 from my dad. I have been looking at two film cameras lately, the Pentax MG and the Canon AE-1. If I buy the Pentax MG I know I can use the lenses. If I buy the Canon AE-1, can I still use these two lens? Or do I need to use an adaptor?
You need an adapter to mount Pentax K-mount lenses on any Canon camera body. The AE-1 is a Canon FD mount, so a search on Google for Pentax K to Canon FD will give you what you want.
You will not find a Pentax K lens to Canon fd camera adapter. The other way around yes, but I have looked everywhere, B&H, ebay, etc. Don't let these guys mislead you. They can't be found. If you buy an AE1 you will not be able to use your Pentax lenses.
An adapter is all you should need. B&H (bhphotovideo.com) has nearly every camera-lens adapter you can find. For example, you can get a $10 adapter canon to nikon, but you lose autofocus. if you really feel the need, you can spend $100-$300 and use autofocus.
I recently made an adapter using an FD body cap and a PK lens mount. http://anaussiebrekkie.com/2017/03/22/proof-of-concept-pk-lens-to-fd-body-adapter/
I'm presently using a Pentax 50mm f/1.4 and a Pentax 28mm f/2.8 lens on my Canon EOS 550D with the help of an adapter. Brand name of the adapter is Kiwifotos (jjc). Both of these lenses are great, you will master manual focus with training. The Pentax lenses I have are K mount. Thus I bought a Pentax K mount to Canon EF adapter. You can find them on ebay. but beware there are lot of cheap adapters which wont focus infinity.