I use 3 fifth size strips to model 3/5. I want to use tenth size strips to model an equivalent fraction. How many tenth size strips will I need?

3/5 = 3 fifth size strips

You want to find an equivalent fraction with the denominator of ten, correct? Then you would multiply the fraction in a way that will allow you to have a denominator of ten.

So ...

3/5*2/2=6/10

You would need 6 tenth size strips.