I am trying to build a template for testing and I have to use about 95000 zipcodes. this is in it's own sheet (say, zipcodes)

I am predominently using index/match to look up values but because the zipcode column is in text format to preserve the leading zero's I always get a #N/A error because the format in the zipcode cell; in the results sheet is in number (special custom) format.

My solution is to convert the 95000 zipcodes to number format.

I have tried the following and it hasn't worked:
- highlighted the column (all cells) - changed format to number. But when i use the =istext function against any of these cells, the outcome is "true", as in "it's still text format"
- copied the entire zipcode column, pasted it to another column formatted as a number. Pasted special by keeping number format. This didn't work

The only that does work is if I:
- Convert the column to number format, double click on each cell - but this is not viable to me as I have large amount of data

Is there another way where I can mass the change format of this zipcode column from text to number?

Thanks in advance