Dear Dilip,

this is a simple answer, just download the statistics from the Ministry of Culture, Tourism and Civil Aviation.

The 2022 report is available with this link

https://www.tourism.gov.np/files/NOTICE%20MANAGER_FILES/Setting_Nepal%20Tourism%20Statistic_2022.pdf

Try the UNWTO, the WTTC as wel as the World Bank for more data:

https://www.worldbank.org/en/news/feature/2022/06/03/harnessing-tourism-to-enhance-the-value-of-biodiversity-and-promote-conservation-in-nepal

Good luck