Three wire supply and Four Prong Oven?
If your area uses the National Electrical Code then it has an exception for older installations that allows you to continue to use a 3 prong (NEMA 10-30) receptacle.

The appliance can usually be fitted with a 3 prong plug and the ground and neutrals are bonded in the appliance not at the receptacle.

Get yourself a 3 prong appliance whip from the box store and replace the cord on your oven. Look for information online your model and how to bond the ground and neutral inside the connection box.

Good Luck!