I look up my tax returns for 2017 & 2018, it says I didn't file with Credit Karma in those years. But I have emails from CK that my returns were accepted. Where to find?

City taxes will not show up on a federal return.  You need a copy of the state return if the city taxes are paid thru the state filing.  Otherwise look thru your records for the proof of payment ... a canceled check or CC statement. 

You say you used Credit Karma but you are asking on the TurboTax site about city tax returns from several years ago.   In general,  IF a city tax return can be prepared using tax software it will be done as an extra step when you prepare your state return.  Your city return will not be shown anywhere on a federal tax return; the IRS will not know if you paid your city tax.   And...your only proof that you paid your city or local tax will be your own bank or credit card record.  

 

https://ttlc.intuit.com/community/intuit-account/help/is-credit-karma-a-part-of-turbotax/00/2092900

 

 

 

Going forward, if you use TurboTax and have a city or local tax to take care of:

 

TurboTax only prepares a few city or local tax returns as an extra step in your state return.  For most local tax returns you are on your own.  You may have to ask around amongst your neighbors, etc. to find out if you have a local tax and how to pay it. “Google “ local tax for your area.  Call your city government, etc.  Your only record of paying your local tax will be your own bank/credit card records

 

https://ttlc.intuit.com/questions/1899325-which-city-tax-returns-can-i-do-in-the-turbotax-state-program