That manual will have a diagram showing the fuse box layout and what each fuse controls. Look for fuses related to "power seats," "seats," or possibly even a more general circuit like "accessory power."
If you don't have the owner's manual, you can often find a PDF version online by searching for "[Year] [Make] [Model] owner's manual." Alternatively, you might be able to find a fuse box diagram specific to your Blazer's trim level via online forums dedicated to Chevy Blazers or general automotive repair.
Important Note: Before checking any fuses, always disconnect the negative battery terminal to prevent accidental short circuits.