You can get a free transcript from the IRS:
If you are trying to e-file 2019 for the first time, forget it. You will not be able to e-file it unless it was rejected on October 15, and you are trying to fix it and re-file. You will have to print, sign and mail it instead. If you did try to e-file on the deadline day, you have until October 20 to make corrections and re-file.
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
Federal and state returns must be in separate envelopes and they are mailed to different addresses. Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.