If the model number is correct, there is a small input line filter board with a 125V, 20 AMP line fuse inside the microwave. Its usually mounted on a small input line filter board at the point where the power cord enters the back of the unit. You will need to UNPLUG the microwave oven and remove the exterior case to access. The case comes off in various ways depending on manufacture and model. I found this illustration at pcappliancerepair.com based on the model number you listed this question under:http://pcappliancerepair.com/model-display.php
The line filter is listed as item 1420. The fuse will be mounted to this board.
You can purchase replacement fuses at any hardware store. You can usually purchase a box of fuses at a hardware store for just a little more than what the manufacturer charges for a single fuse. 125V, 20AMP Slow Blow fuses are recommended.
If you have any questions, or need assistance troubleshooting, please post back and let me know. I hope you find this information helpful.
NOTE: Make sure you take any resistance readings with the microwave UNPLUGGED and the component under test isolated (removed) from the circuit.