The microwave light bulb is shown as #75 on the
diagram. You have to pull the microwave out of the oven cabinet to gain access to the part. The
Service manual might help.
- The light bulb (lamp)
Part number: AP3846617 
Here are the breakdown diagrams and
Replacement parts for WHIRLPOOL KEMC308KSS0 | AppliancePartsPros.com
Gene.