Here is the solution:
“Just to confirm, are you trying to convert Microsoft Excel file to Google Docs or Google Sheets?

If you are converting it to a Google Sheets file, the maximum cells that can be used on Google Sheets is up to 2 million cells which includes the amount of blank cells on your spreadsheet. To optimize your spreadsheet, I would suggest to delete blank rows and columns. You can try using COUNTA() and COUNTBLANK(). This should add up all of the cells that are empty and non-empty if added together.

If possible, break the spreadsheet down into smaller sheets by having a master spreadsheet and referenced spreadsheets. You can use IMPORTRANGE() function to import cells from one spreadsheet to another.”