The FAA puts out recommendations for the speed at which you should fly when remaining in the pattern. They have no recommendation for the downwind leg, but they do for base and final.
According to the Airplane Flying Handbook, when you turn to your base leg, you should transition to a speed of 1.4 x Vso.
For example, if your landing configuration stall speed (Vso) was 50 knots, 1.4 x Vso would be 70 knots. So 70 knots is the speed you’d fly your base leg.
On final, the FAA recommends that you fly 1.3 x Vso. So say your best final approach speed the FAA recommendation would be 52 knots (1.3 X 40). You’d fly fly 52 knots on final.
The aircraft manufacturer’s recommended speeds though would override the FAA’s recommendations, if you are able to find the manufacturer’s information for the aircraft you’re flying.