Using an If function, how do I change string of text in dataframe to another string?

Question

using the following dataset

 structure(list(...1 = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 3, 4, 5, 6, 7, 8, 
9, 10