According to both the Peel commission and the 1946 British survey, there was basically none. “Arab illegal immigration is mainly casual, temporary and seasonal,” said Peel, and the 1946 survey states “"… the expansion of the Moslem and Christian populations is due mainly to natural increase…"

The Jewish Historian Roberto Bachi estimates only about 900 Muslims per year immigrated between 1923 to 1946.

Where did the increase come from? According to the British register of Births and Deaths, it came from a natural net increase of 2.7%. (One of the highest recorded birth rates of all of the British controlled lands at 5%, and a high mortality rate of 2.3%.) In fact the estimated number of Muslims in 1947 is simply the number in the 1933 survey plus the net gain.

Peel: https://biblio-archive.unog.ch/Dateien/CouncilMSD/C-495-M-336-1937-VI_EN.pdf

1946 Survey: Population in Palestine and the Increase in Population. British Mandate: A Survey of Palestine: Volume I

Bachi: http://www.cicred.org/Eng/Public...

Vital Statistics figures from The Fertility and Mortality of the Population of Palestine, By: Hinden, Rita. Sociological Review (1908-1952). Jan/Apr40, Vol. 32 Issue 1/2, p29-49.

You seem to get all your information from Israeli propaganda with no verifiable sources.