Step 1) Create 3 circles whose radii are 10,20 and 25 MM . Make sure it’s fully defined (no blue) .

Step 2) Extrude the outer rim :

Step 3) Create a new sketch on the face of the outer rim. Call this sketch “sketch on face”:

Step 4) Create an extrude on this plane. You can do whatever you like, below is one example of it could look like: