If you’re not opposed to it, it’s in the AUR.
Edit: Sorry a more helpful answer is that you can likely find it in manjaro’s add/remove software application. Optionally, From the command line you would execute pamac search syncterm
if it exists pamac install syncterm
Here’s the documentation for enabling AUR: https://docs.manjaro.org/activating-the-aur-and-building-packages-with-pamac/
Edited my response to be more helpful.