I want to change home currency from PKR to AED and conversion rates of USD,EURO accordingly? Kindly suggest

Do you have a QBO Global version for Pakistan account or QBO UAE version?

https://quickbooks.grsm.io/Pakistan

 https://quickbooks.grsm.io/Arab-Emirates

Afaik, you are only allowed to change the home currency prior to register any transaction data. Your plan is also supporting multi-currency transaction. 

As additional option, explore this 3rd payment service to deal with multi-currency transactions. You may release and get paid in your local currency and your customer will pay it in their local curency.

https://veem.grsm.io/veems