Mammllaria (elongata)

Thank you hablu. I have 2 more questions

1. should I repot it

2. Should the plant be separated into 3 or 4 smaller plants?

Yes, you should repot it. Don't divide it. Carefully take it out of the pot y and clean most of the soil from the roots, often there is soil around that will not come off, don't worry about that. Get another pot bigger by about an inch across the top. Make some cactus and succulent soil with 1 measure potting soil and 1 measure pumice or perlite. Plant the cactus letting the soil only come up to cover little more than the roots. The top of the soil should be 1/4 tp 1/2 an inch from the top of the pot.