@sep9001 Lightroom is really meant to be a catalogue with built-in adjustment tools.
Best possible option is to click on the
Adjustment Brush (or press K).
If needed, adjust the brush size.
Run the brush over the plate (don't worry about what is happening, we'll get to this in the next step)
Adjust the following to maximum...
- Exposure
- Contrast
- Hightlights
- Shadows
- Whites
- Blacks
Just move the sliders all the way to the right, one after other, until you've made it look so washed out that the text could not be seen.
By the way, that worked for the front white plate as I have done it, but I haven't tried the rear yellow plate, so you'll have to try adjusting those settings to see what you can do.