It's likely that either (a) you customized your work environment prior to Goodies installation so that it isn't showing where it wants to be in the menu structure, (b) you installed an update to AC 26 after the initial installation and need to re-install it to update the 3D Studio In add-on so that it is recognized , or c) there is some incompatibility (that I cannot imagine) with the EDU version.
Go to Options > Add-On Manager and verify that you see 3DStudio is listed and with a checkmark. When you click on it, what do you see in the "Add-on Info" panel - where in my screenshot it shows where it is in the menu structure (and it is indeed there)?
Was Archicad running when you installed it? If so, that could be the issue. Quit AC, relaunch and see if it is there? If still no, Quit, re-install Goodies, then relaunch...?
One of the forum moderators • AC 26 USA and earlier • macOS 12.6.1, iMac Pro 10-Core, Radeon Pro Vega 64