Whenever Windows installs an update via Windows Update, it will log this in its windowsupdate.log file. PowerShell can then parse this file. You should use this to find out how many updates you received on which dates:
Get-Content $env:windir\windowsupdate.log |
Where-Object { $_ -like '*successfully installed*'} |
Foreach-Object { $_.Split("`t")[0] } |
Group-Object -NoElement
Where-Object { $_ -like '*successfully installed*'} |
Foreach-Object { $_.Split("`t")[0] } |
Group-Object -NoElement
It then reads the log file, selects only lines with the keyword "successfully installed," extracts the installation date, which is the first tab-separated part of each line, and groups the results.