The goal of babelmixr is to convert nlmixr syntax to other commonly used tools.
If decide to submit to CRAN, you can install the released version of babelmixr from CRAN with:
install.packages("babelmixr")
Otherwise you can always install from github:
remotes::install_github("nlmixrdevelopment/babelmixr")
After installed, if you use the standard interface, you can convert to monolix with
mod <- nlmixr(nlmixrFun, nlmmixrData, est="monolix")