Hi!
Assuming you added two "Initialize variable" action blocks, both type string, names PostDate and ExpirationDateOfPost, values the dates you wanna take as the limits, both of them in the format yyyy-MM-dd.

Now on your 'Get items' action block you can define an ODATA filter on 'Filter query' input (you need to click 'Show advanced options' to see this input) by typing the following:
InternalColumnName gt '@{variables('PostDate')}' and InternalColumnName lt '@{variables('ExpirationDateOfPost')}'
Just replace 'InternalColumnName' with the one corresponding to your target column in your Sharepoint List
GReat article on ODATA filters for Sharepoint here
https://sharepains.com/2018/11/12/sharepoint-get-items-odata-filter-query/
Not in my laptop, unable to help