I can't find my xstudio_measured_integrity.dat file?

It depends from the OS of your computer.

The best is to activate the traces then, run a integrity check from the menu (Tools> Check database integrity).
When the integrity check process is completed, check out your traces to see where is saved the xstudio_measured_integrity.dat file:

...
{00:00:08.617} [thread utils  ]  theoretical database description nb characters: 75740

{00:00:08.617} [thread utils  ]  destination folder: C:\\Users\\Paul\\AppData\\Local\Temp
{00:00:08.627} [write file    ]  writing in once in xstudio_measured_integrity.dat...

{00:00:08.627} [write file    ]  setting write file to xstudio_measured_integrity.dat...
{00:00:08.627} [write file    ]  deleting file C:\\Users\\Paul\\AppData\\Local\\Temp\\
                                 xstudio_measured_integrity.dat...
{00:00:08.627} [write file    ]  writing in file C:\\Users\\Paul\\AppData\\Local\\Temp\\
                                 xstudio_measured_integrity.dat...
{00:00:08.627} [thread utils  ]  generated measured integrity file: C:\\Users\\Paul\\AppData\\Local\\Temp\\
                                 xstudio_measured_integrity.dat
{00:00:08.627} [thread utils  ]  sending email about integrity...
{00:00:08.627} #thread        #  constructing thread...
...