I paid a nanny a total of $2,100 all through 2019. But some of that went towards medicare tax & Social Security tax. The problem is i don't know the amount

[KatrinaB48]

Assuming you withheld the required amount, then you can just multiply to determine what you withheld. Since you paid your household employee cash wages of $2,100 or more for 2019, you should have withheld 6.2% of Social Security and 1.45% of Medicare taxes (for a total of 7.65%). You should have also paid your share of Social Security and Medicare taxes, which is also 7.65% of cash wages. 

Note: You should convert the 6.2% to decimal form (.062) and the 1.45% to (.0145) then multiply to determine the amount of tax withheld.