Sorry misunderstood. I usually use the API and rarely use the summary files.
Go to
https://data.census.gov/table?q=B01001
You will see the table name B01001 AGE BY SEX
under that you will see "2021 ACS 1-year estimates Detailed Tables"
to the right of this is a little downward pointing arrow - click on it
use the pull down menu to select 2019 ACS 5-year Estimates Detailed Tables
Dave