I am replacing my oven. I have a 50 watt breaking that the current oven is using. I do not know what size the new oven needs. Is it okay to use this breaker.

You likely mean AMPS, See what the oven requires, use the wiring and breaker needed to protect the wiring.
Wiring can be larger that required, breaker should be rated for oven and no larger than than wire it is to protect.