I had 10% of my unemployment withheld for taxes and I forgot to claim that how do I get that $2,100 that I paid in taxes back

You will have to amend the 2021 tax return for the 2021 unemployment income and the taxes withheld.

See this TurboTax support FAQ for amending a prior year tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-already-filed/L4VjJ9BA2_US_en_US?uid=ld1n99kr