mutate() takes a data frame as its first argument (the thing passed into the pipe). I don’t understand the goal of the assignment paste0("data2_1",i) <- paste0("data2_1",i), but the result is a character string, not a valid reference to a data frame.
For clarification, do you mean data frames here? (data frame = an R object; data base = an external system for data storage, such as MySQL)
Is there any way you can come up with a small reproducible example of the sort of thing you’re trying to do? I think it will help people better understand your problem and suggest better solutions. (Complete reproducibility can be hard when databases are involved, but as close as possible is still helpful)