$ dollar sign missing

Select the column or measure in data view.  On the ribbon at the top you will see formatting options.  There will be a dollar sign there (and lots of other currencies in the dropdown).

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thank you HotChilli it's working now.👍

Adding a dollar sign ($) or any currency symbol to a filed power bi for formatting purposes is typically done in the Modeling or Fields pane. 

In the Filed pane, find the field that you want to format with dollor sign, This is a typically a numeric field representing a currency amount. 

In the PBI ribbon at the top, click on the modeling tab, this tab contains options of data modeling and formatting, In modeling you should see a format section, and you will find number formatting option in that you should see currency symbol. 

Here, you can specify the currency symbol you want to use. Also, by default, it's set to the dollar sign.