The vast majority of modern microwave ovens do not use fuses that need regular replacement by the user. Instead, they are equipped with a thermal cutoff or thermal fuse, which is a safety feature designed to prevent overheating and potential fire hazards. These thermal cutoffs are typically built into the microwave's internal circuitry and are not user-replaceable.
If the thermal cutoff or fuse fails, it's not something you should attempt to replace yourself. Tampering with the internal components of a microwave can be dangerous and may void any warranties you have. Instead, if you suspect an issue with your microwave oven, it's best to contact the manufacturer or a qualified appliance repair technician to inspect and repair it.
In the event of any malfunction with your microwave oven, such as it not turning on or not heating food properly, it's safer to have it professionally checked and repaired. Regularly cleaning and maintaining your microwave can help extend its lifespan and ensure safer operation. If you have specific questions or concerns about your microwave oven, always refer to the user manual or reach out to the manufacturer for guidance.