If the model number is correct, there is a 125V, 20 AMP line fuse inside the microwave. Its usually mounted at the point where the power cord enters the back of the unit. Unfortunately, you will need to uninstall the oven (if this is an over the range model), UNPLUG it 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 fuse is listed as item 12 (part number 56001353). Keep in mind, there are different vairations on the model number you provided. You need to look at the model number you have and include the last three letters as well. I reviewed most of these models and they appear to all have the same parts.
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 Ceramic Slow Blow fuses are recommended. If you wish to order on line, use the part numbers to search by comparison as the model number you listed this question under may not be available at all the websites I have provided. The parts, however, ARE listed.
If you have any questions, or need additional 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. These ovens can blow a fuse by simply sitting idle. This can occur from any power fluctuations, brown outs, voltage spikes, etc. Or, it could be the symptom of a component that may have failed. If you find the internal fuse blown and replace it, only to have it blow again, you have a more significant problem than a simple blown fuse.