Excel worksheet to CSV file - retaining number format

Background: I'm taking an excel worksheet of product data and converting it into a csv file to upload into a Point of Sale (POS) program.

Problem: I'm having difficulty with the numeric values for product bar codes. A cell in the excel column with the barcode data shows, for example, 881934185489 but when converted to a .csv file the number content is converted to 8.81934E+11. "8.81934E+11" is of no use in the POS system. How do I retain the full 12 digit numerical display in the csv file?

Note: I am not a proficient user so please keep replies / solutions as plain and simple as possible. Thanks.

if your POS system doesn't care if the value is passed as a number, you could convert the number to text. You can do that by simply putting a ' before the number.

Thanks Simi. Unfortunately the POS system does care and does require the data to be a number. Given there are over 5300 line items in the file I really need to find an elegant, automatic solution. Formatting as "General" does not work as it gives the truncated 8.81934E+11 value. Formatting as "Number" does not seem to convert cleanly into .csv format. Neither does formatting the excel worksheet as "custom" and then saving as .csv. I suspect this is a MS issue. I just hope there is someone who has found a resolution they are willing to share.