Need Expression in DAX

Kavya123 So many questions. Are your Customer and Sales tables related to one another? If so then you should be able to do something along the lines of:

Measure = CALCULATE(SUM('Sales'[Sales]),'Customers'[Product]="Shoe")

If that doesn't work...Sorry, having trouble following, can you post sample data as text and expected output?
Not really enough information to go on, please first check if your issue is a common issue listed here: https://community.powerbi.com/t5/Community-Blog/Before-You-Post-Read-This/ba-p/1116882

Also, please see this post regarding How to Get Your Question Answered Quickly: https://community.powerbi.com/t5/Community-Blog/How-to-Get-Your-Question-Answered-Quickly/ba-p/38490

The most important parts are:
1. Sample data as text, use the table tool in the editing bar
2. Expected output from sample data
3. Explanation in words of how to get from 1. to 2.