Is there a unique ID per instance of a plugin?

is there a id number for every instance of vst3 called in a daw ?

Sorry, I don’t understand. Can you be more specific about your question? Maybe it helps if you describe the use case you have in mind?

when a vst3 is called in a daw a new unit is created ,
i have to identifie the unit in the code to change some parameter process.cpp .
the plugin at the first instance do somthings , the second do somothing different and so on…(until instance 128 in my case)
is simple to create a global variable that is incremented by one if other instance is created but is impossible (without vst function) to differenciate the instance from eachother, i want to assign to each instance a number id (0-127)

As far as I know this is not something that is allowed. VST3 instances (including instances of the same plugin) are not allowed to share data between them. If you could share an ID, then you could share anything else.

For sure Is allowed ti share data between unit example :
Fabfilter proq3 vst3 for example share the data of each track to other proq3 to analyze the spectrum.

Yesterday i resolve this problem

Yes you could use shared memory to exchange information between plugin instances, you have to take care that you are in the same process and not instantiate in different process (sandboxing) in this case use IPC (InterProcess Communication)