MERGE 2 DATASETS PLEASE. I require assistance in consolidating multiple datasets

MERGE 2 DATASETS PLEASE.
I require assistance in consolidating multiple datasets within STATA. Specifically, one file comprises merged data from 2015, 2018, and 2021, while another file details the Variable A4A (ethnicity). This variable is present in the datasets for the years 2015, 2018, and 2021.
A4A_new_w appears like this in the PUBLIC DATASET:
A4A_new_w (8) Ethnicity
Measurement Level: Scale
Column Width: 8 Alignment: Right
Print Format: F2
Write Format: F2
Value Label
1 While Alone NH
2 Non-White
But the restricted data has this outcome:
A4A (11) [ETHNICITY]
Measurement Level: Nominal
Column Width: 8 Alignment: Right
Print Format: F2
Write Format: F2
Value Label
1 White non-Hispanic
2 Black non-Hispanic
3 Hispanic (alone or in combination)
4 Asian/Pacific Islander non-Hispanic
5 Other non-Hispanic (American Indian, Other, 2+ ethnicities)
Upon requesting the restricted data file, I received the following instructions: “The variables you requested for 2015-2021 are consistent across all NFCS waves from 2009 to 2021. They can be appended to the NFCS dataset using the NFCSID indicator.”
My objective is to ensure that the datasets for 2015, 2018, and 2021 accurately reflect various ethnicities, rather than simplifying them to “white” or “non-white.”
Should you have any questions or require further clarification, please do not hesitate to contact me.