Excel_prefixed with 0 and how to concatenate those columns in excel

https://www.icts.uiowa.edu/confluence/display/REDCapDocs/Preserving+Prefixed+Zeros+in+Excel
with the help of the above link i prefixed the 0 in excel.

Now i want to concatenate these columns A &B to C.

Please let me know how to do that.

Example:
column A      column B           column C
06789         00054              Expected: 0678900054
                                 Actual:   0678954

Remember that concatenating numbers is actually concatenating the underlying number (6789 and 54 in your example) not the formatted string.

You can do what you want using:

=CONCATENATE(TEXT(A1,"000000"),TEXT(B1,"000000"))

where “000000” is the formatter you applied.