Is there a Photoshop product that I could use to scan slides used in a projector and have them be viewable online? These slides are 30-40 years old? Can this be done, or am I barking up the wrong tree?
Are they 35mm slides?
If so, you don't really need any software [Adobe's or anyone's], you need a scanner, which will have software with it. Ideally, you should get a slide scanner, but many flatbeds come with an adapter.