How can i get rid of all the cancer sores inside my mouth?

Canker: I assume you mean canker sores. There is no way to get rid of them. They run a course, usually 7-10 days. There are otc meds to treat them palliatively as well as prescription meds to lessen the duration. Eliminating stress, trauma, sometimes spicy foods can lessen the occurrence. Some people are just more predisposed. If you do mean cancer sores see your md.

Canker?: I hope you don't mean cancer! some will try lysine tablets, baking soda, rinsing with equal parts kaopectate / liquid benadryl (diphenhydramine)...But difficult to make go away forever.