Hi @Muhammad Noman Sohail ,
Click "follow" the shrepoint site from which you want to copy the list. Then refresh the site which you want to create a new list, and you will find that the site you just followed appears under "Select a Team or site" .
If you are the person who created the site – it automatically makes you follow it. If you were not the person who created a site, just click the Follow button in the upper-right-hand corner of the site(as shown below).
In addition，“Save List as Template” is missing in SharePoint Online modern sites. But you can use PowerShell to fix it.
If you need, you can refer to this link: https://www.sharepointdiary.com/2017/08/sharepoint-online-save-list-as-template-missing.html
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