To find the correct fuse, you must consult your owner's manual. It will have a fuse box diagram showing which fuse(s) are related to the wipers/washers. The diagram will show the amperage rating of the fuse, which is important if you need to replace it.
If you don't have the owner's manual, you can often find a downloadable PDF version online by searching for "[Year] [Make] [Model] owner's manual PDF".
Troubleshooting Tip: Before replacing the fuse, make sure the washer fluid reservoir is full. A low fluid level will also prevent the system from working. Also check the pump itself for any obvious blockages or damage.