If you're getting "can't find file" errors in Excel, there are a few things you can do to try and fix the issue.
First, make sure that the file you're trying to open actually exists. Check the location where you saved it and see if it's there. If it is, try opening it from a different program to see if that works. If not, the file may be corrupted and you'll need to try and repair it.
To repair a corrupted Excel file, open a new workbook and go to File > Open. In the "Open" dialog box, select the file you want to open. Click the drop-down arrow next to the Open button and select Open and Repair. This will attempt to repair any errors in the file.
If that doesn't work, you can try using Microsoft's Office File Repair tool. This is a free tool that can help repair corrupt Office files. Just download it and follow the instructions to run it on your file.
If none of these options work, then unfortunately the file may be beyond repair and you'll need to start over with a new file.