Formula Required if possible

You could use nested IF functions, but that's messy.

If those are the only three values you will ever find in C8, I suggest the IFS function:

=IFS(Sheet1!C8 = "CASH", "CASH",
     Sheet1!C8 = "NIL", "NO PAYMENT",
     Sheet1!C8 = "EFT", "ELECTRONIC FUNDS TRANSFER (EFT)",
     Sheet1!C8 = "", "",
     TRUE, "[something else]"
)

(The extra spaces and line breaks (Alt+Enter) are completely optional.  I include them for ease of reading.)

The comparison of Sheet1!C8 to an empty string is my presumption on what you want, as is the last Boolean test (TRUE, which covers all other possibilities).

Of course, if you might have other valid values in C8 in the future, it would be best to put a cell range or Excel table with those valid values and their counterparts somewhere, and use the XLOOKUP function to do the translation.