How to add business manager to partner account of fb page of another business via Facebook API

i am trying to add a business manager to the partner account for another business page via facebook api, i have tried several apis, but failed. I want to grant access to facebook page.

Below are some of the apis i used in postman:

https://graph.facebook.com/v17.0/page-id/assigned_users?user=TO_WHOM_PERMISSION__WILL_BE_GRANTED&business=PAGE_BUSINESS_ID&access_token=TOKEN_OF_PAGE_OWNER&tasks[]=MANAGE https://graph.facebook.com/v17.0/BUSINESS_MANAGER_ID/owned_pages https://graph.facebook.com/v21.0/BUSINESS_MANAGER_ID/managed_businesses?existing_client_business_id=BUSINESS_ID&access_token=TOKEN_OF_OWNER 

But nothing worked, My main motive is to give access of facebook page to some other business manager by adding him to partner account, Do anyone have any idea how it can be done via api, any small help will be really appreciated, thanks in advance !!!