Need to pull out all sharepoint site id using Graph API

Question

I’m just trying to construct the Graph URI for the trim existing version delete job. In the location variable, I’m just trying to pull out all the sites that match the $hostname. I really have no idea what command I need to use on the $loc variable to pull out all the sites ID across the geo's

$URI = https://graph.microsoft.com/beta/sites/$hostname`:/$loc

Could any one advise on this ?