Everybody can read about that in their transparency report on their website

https://threema.ch/en/transparencyreport

And they give out 2 Informations about a Threema-ID:

1. Date (without time) of the Threema ID’s creation

2. Date (without time) of Threema ID’s most recent login

These are the ONLY 2 Information they store!

The following information is only available if the user has chosen to use the respective optional functionality:

Only in case the user in question has chosen to link a phone number and/or email address with their Threema ID: Hash of the user’s phone number and/or email address

Only in case the user in question has chosen to use a third-party push service (and their ID was active within the last three months): Push token

So what....