@thepondperson I'm not sure that particular filter will work with your pump -- it's a pre-filter that's made to fit on the intake part of the pump and the pump you showed isn't designed the same way. See picture.
View attachment 95094
A pre-filter is to protect the pump from dirty water that gets sucked into it. It's a good thing to have because it protects the pump, but I don't think think the one you showed is going to work with the pump you showed.
Do you want a filter that CLEANS THE WATER? Then, what
@Ruben Miranda suggested is a good choice, but might take up a lot of room in your 40 gal tub.
Again, please be more specific and tell us what you are wanting to do. You keep asking for us to link you to things, but we can't do that unles we know what your purpose is.