Those who use a sinner's prayer use Romans 10:13 as justification for it.
But Romans 10:14 clearly shows that no one can call upon the name of the Lord unless they have believed, hence they are saved.
So, no one has to ask Christ to save them.
The prayer they can say is a prayer of thanksgiving for God saving them.
Now they can cry Abba Father!
The sinner's prayer is a soul winner's gimmick used to keep 'score' of souls 'won'.