When did Moshe Daven this Tefilah?
Rashi: Refer to 9:25:1:1 and note. 1
Ramban: It is synonymous with the Tefilah that Moshe Davened 2 before descending Har Sinai the first time - following which the Torah wrote there 3 "Vayinachem Hashem al ha'Ra'ah ... ".
See also Oznayim la'Torah DH 'Va'esnapal lifnei Hashem' #1, citing the Ha'amek Davar, who explains Rashi. Refer to 9:26:2:1.
Which the Torah cites - in Ki Sissa Sh'mos, 32:11-13.
In Pasuk 14.