The IRS shows they already sent it to you. Double check your bank statements. It came out back in March-May 2021. Did you get it? Line 30 is only if you didn't get the full amount or qualify for more.
If the IRS thinks they sent it to you but you didn't get it request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
