The 1040SR is a new form starting in 2019. The 1040SR is the same as the regular 1040 just larger type. Same line numbers. You automatically get the SR if you are 65. If you are using the Desktop program there is a way to force the one you want.
1040SR
https://www.irs.gov/pub/irs-pdf/f1040s.pdf
1040
https://www.irs.gov/pub/irs-pdf/f1040.pdf
