In my story, one of the characters essentially possesses something akin to true invulnerability and is essentially immortal due to [redacted]. In this part of the story, a group of terrorists with stolen sci-fi grade technology use it to open a tear in space-time right next to said character, a tear which creates a portal between his current location and a point in space at 10 meters away from an artifical (man-made) black hole's event horizon. This causes the character to be sent into space and sucked into the black hole.
The main scenario is: said character, due to [plot-armor] his composition, manages to not end up reduced to another chunk of compressed matter, and thus he is left trapped inside the black hole until it completely evaporates.
The problem: I'm having trouble stipulating the size and mass of the black hole, since I'm not very knowledgeable and I'm yet to comprehend how to use the black hole calculators I've found. I want this black hole to last a reasonably long time for human standards, but no more than 10000 years. Is there any easy(ier) to understand black hole calculators that I could use to have a better idea of its mass and size? In the scenario in question the black hole would be positioned in a place where, ideally, it wouldn't gain any additional mass other than what it had the moment the tear was open.
(this isn't the last time I plan to use black holes in this story, so I'm in need of a simpler calculator until I can understand more about them. )