You can use Dynamics 365 > Find labels… in Visual Studio to find D365FO labels, but its capabilities are quite limited. Sometimes a better option is searching through the underlying text files directly and you can easily automate it with Powershell.
The following script looks at all label files for US English and finds all labels containing either PowerBI or Power BI. It skips label comments, because you’re typically interested only in labels and not their comments.
$packagesDir = 'C:\AOSService\PackagesLocalDirectory\'
$labelFiles = ls $packagesDir\*\*\AxLabelFile\LabelResources\en-US\*.txt
$labelFiles | Select-String -Pattern '^(?! ;).*=.*Power ?BI' | select Line, Filename, LineNumber
You might think this approach will be slow, but it actually returns result very quickly.