I miss being poly and my former partners, but I don't know how to tell my wife without making her feel bad.
What does it mean "to be poly"?
It means being in a relationship with multiple partners.
It may be hard to do, but you should be honest with your partner. She deserves that. Trust that your relationship can handle it.
I need to tell her that I want to be in a relationship with multiple partners and see her reaction first. I know that much already.
Its good you have come to that conclusion about the relationship. Only then will she try and make sense of the situation. If she doesn't understand then find someone else who will.