Are you getting the UPS stats on the dashboard of your UNRAID server, like this?
If not, then you probably have some additional configuration to make sure that data is being received in UNRAID, if your UPS is capable of reporting and already connected to your UNRAID server via USB. That's done on the Settings page under Systems Settings | UPS Settings.
My recommendation would be to comment out that line until you have telegraf up and running - then you can experiment with changes to telegraf.conf and adding back in additional plugins by un-commenting those lines.
Don't be afraid of editing the telegraf.conf file, it's pretty simple. Most of it is just un-commenting sections that you want to add and changing default values/addresses to match your system. Just make sure you make a backup copy of a known working config file before you start editing, in case you need to roll back. And, after each change you will either need to restart the telegraf service from the terminal, or restart the docker, to incorporate the change.
Depending on your level of interest in Grafana/Influx, I found it very helpful to use InfluxDB Studio running on a Windows PC to see all of the measurements that were being stored in the database. That let me see what was being recorded by telegraf in the database, which helped troubleshoot areas where I wanted to customize the UUD and other dashboards in Grafana.