Have a 40amp breaker for my dryer what resptical do I get 30amp or 50amp

What kind of dryer is it? Typical residential electric dryer?
Why is there a 40A breaker? Who installed it?
What size wire is the circuit, and how many conductors run?

A typical dryer circuit is #10cu wire with a 30A breaker.

This is what I'm going to do put 30a breaker in and a 30a outlet in and this will do it?

This is what I'm going to do put 30a breaker in and a 30a outlet in and this will do it?

Let's do this the proper way. Please check the electrical specs in the user's guide for your dryer.

It will tell you the requirements for the electrical circuit for that model of dryer.

This is what I'm going to do put 30a breaker in and a 30a outlet in and this will do it?
Well, since you avoided all the questions posted so we can clarify, all I can say is, if this is a typical residential electric dryer you need a 2-pole 30A breaker, 30A 4-wire (NEMA 14-30) receptacle, 10/3 cable, and a 4-wire dryer cord.