.ink is the file extension for shortcuts. It isn't the excel file you need. Check again for the .xls file with Undeleter.
If you want to convert it anyway, open a folder, click organize, click 'folder and search options', under the view tab uncheck 'hide file extensions for known file types', Click through any prompts(if any appear), Click OK, then go to the file and replace
the .ink with .xls.
NOTE: there is a 99.9% chance that the file you found is a shortcut to the file you need and will probably give errors when to try to open it after converting the file type to .xls