You can start with this document on how to see the amount spent on Azure resources on Azure Portal:
To review your costs in cost analysis, open the scope in the Azure portal and select Cost analysis in the menu. For example, go to Subscriptions, select a subscription from the list, and then select Cost analysis in the menu.
Let me know if you have any questions.
If you are seeing any error accessing this on Azure Portal, please share the screenshot/error message.
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