John Gill Commentary 2 Chronicles 2:17

"And Solomon numbered all the sojourners that were in the land of Israel, after the numbering wherewith David his father had numbered them; and they were found a hundred and fifty thousand and three thousand and six hundred." — 2 Chronicles 2:17 (ASV)

And Solomon numbered all the strangers that were in the land
of Israel
Which, according to Kimchi, were the remains of the Amorites, Hittites, Perizzites, and Jebusites, see (2 Chronicles 8:8) , yet not idolaters, or they would not have been suffered by David and Solomon to have dwelt in the land, but were such as were become proselytes of the gate:

after the numbering wherewith David his father had numbered them ;
not at the time Israel was numbered by him, but in order to provide workmen for the building of the temple, (1 Chronicles 22:2) ,

and they were found an hundred and fifty thousand and six hundred ;
men able to bear burdens, and hew timber.