Hi! Welcome!
The error message is telling you that you don't have the R6 package installed, which tidyverse depends on (or more precisely, one of its sub-packages depends on, since tidyverse is a sort of meta-package that loads other packages).
You can run install.packages("R6") to fix this dependency, but there may be more dependencies missing that you would then have to install one by one after a similar error message. So you might also try install.packages("tidyverse", dependencies = TRUE) to get everything. (But be prepared: this might be quite a few packages!)