How to know "domain-specific Zoho Accounts URL" to generate access and refresh tokens

How to know "domain-specific Zoho Accounts URL" to generate access and refresh tokens

Hello There,

I am working for a european client to get sales orders and invoices in their backend system and I am using PHP as language. I am having trouble to get access/refresh tokens as I am confused or lets say dont know the "domain specific zoho accounts url" to be used !

Can anyone please tell me how to know the domain specific URl for my client ? Let me know if you need anything from me !

Also I am confused which service to use for retrieving the sales order and invoices of my clients ! What should I ask my client to provide as I can see client id and client secret I can use on my own ? No, is organization id is enough to get my client's sales order and invoices once I get authorized ?

Thanks in advance !
Raju