Hi Mari

I assuming you are referring to numbers on the source side?
Typically the formatting you see on the source text, cant be changed once in Studio.
I am not aware of a "find source numbers" and replace with "highlight source numbers"

While I dont fully understand what your objective is, I do have some options you can explore:

1. Import revised source formatting 

If you have a file with lots of numbers, I would explore what can be done in the native source file format as a temporary measure.
Example in MS word do a find all numbers and replace with highlight.

CAUTION: But this would pollute your TM with unwanted highlighted tags and could complicate QA for target side

2. Filter for all segments that have numbers

By using the built in Advanced Display Filter, you can filter for all segments that have numbers.

See my example where out of 35 segments I can take care for the 13 segments that have numbers

3. QuickPlace

Quickplace should always help you identify and recognise numbers within a segment as noted in my example with the blue underline

This is managed as part of having a TM referenced during translation

4. Protecting Numbers 

If you are worried about numbers because they don't need to be managed/changed in anyway then there are a few options

4.A TM Anonymizer

There is an app that allows for you to create a rule by which all hits are then tagged.
In my case all numbers get tagged and therefore its unlikely they will be mishandled 

4.B Verification

We have verification QA settings that will help ensure content is well managed, regardless if its numbers or tags.
Options for this is under File - Options - Verification or Project Settings - Verification 

4.C Advanced Number Checks

If your numbers are complex and you want to have additional assurances they are well managed once in Studio, may I recommend an additional QA that can be downloaded from our RWSAppStore called Number Verifier found here: https://appstore.sdl.com/language/app/trados-number-verifier/440/

Hope my points are relevant and helpful. If not please can you explain your concerns in more detail so I can continue to support you
Have a good day

Lyds