It is not entirely clear what you are doing given that we don't know what first_path looks like and we don't know what the function renamefiles() does.
I will say that when you use list.files it returns a vector that can be iterated over just like any other vector or list.
In addition, there is already a base function for renaming files (file.rename) if you weren't aware.
Also, it looks like your code was not formatted correctly to make it easy to read for people trying to help you. Formatting code allows for people to more easily identify where issues may be occurring, and makes it easier to read, in general. I have edited you post to format the code properly.
In the future please put code that is inline (such as a function name, like mutate or filter) inside of backticks (`mutate`) and chunks of code (including error messages and code copied from the console) can be put between sets of three backticks:
```
example <- foo %>%
filter(a == 1)
```
This process can be done automatically by highlighting your code, either inline or in a chunk, and clicking the </> button on the toolbar of the reply window!
This will help keep our community tidy and help you get the help you are looking for!
For more information, please take a look at the community's FAQ on formating code