Your Adjusted Gross Income (AGI) is found in different places for different years. 

If you are trying to find your 2019 AGI, you can get this information a couple a different ways:

• If you filed your 2019 taxes with TurboTax, sign in and go down to Your tax returns & documents. Select View adjusted gross income (AGI).
• If you didn’t file your taxes with TurboTax in 2019, the best place to get last year's AGI is from the 1040 form you filed with the IRS. Look on page 1, line 8b. 

I received an email about amending my federal tax return for the American rescue plan. I dont know what to do? how to i find this yrs AIG

Is it about unemployment?  Why do you need the AGI?

If you already filed and didn't get the 10,200 unemployment exclusion you do not need to amend.  The IRS will be adjusting it for you.  See,

https://www.irs.gov/newsroom/irs-to-recalculate-taxes-on-unemployment-benefits-refunds-to-start-in-m...

You can log back into your return and it should automatically update your return and show you the new refund.  But the updated return won't be sent.  The IRS will adjust it for you.

Find your current year AGI 

https://ttlc.intuit.com/community/agi/help/where-can-i-find-my-current-year-agi/00/26310