import Excel data with empty cells

I downloaded all the data of the World Bank and now I have almost 100 excel files with one million rows and I wanted to save all these excel files together in one postgresql file. The lines of these files are the names of the series and the columns are the years. For some series, you don't have data in some years and the cell is empty. When I select the column type as an integer, I get an error for empty cells.

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I set the data type to integer for the years columns and got the following error in empty cells. In Excel files, when there is an empty cell, ".." is placed in the blank space