It is a four pin threaded connector. The base is 20mm x 20mm and the round part has a 12mm diameter.
Hello agault,
Welcome to the DigiKey TechForum.
There are many connectors that may match up to 12mm, and 4 positions, threaded.
We will need some pictures of the connector, to be able to try and match it up.
Also, the part number for the stepper motor may help as well.
Hello,
Thank you for the follow-up images.
Here is a link to our closest options based on the information so far :