[P] Uptraining a pretrained model using company data?

Hey guys, I'm doing a (hypothetical) project where I want to uptrain a pretrained LLM on a ton of unstructured customer data for a huge company. The idea being that it then serves as a knowledge base on customers from all sources of data, which can be used for hyperpersonalisation (e.g product matching, content generation etc).

I'm confused about the uptraining part - if I'm trying to make it 'learn' customer data, do I use fine tuning, prompt tuning, or …

customer customer data customers data hey knowledge knowledge base llm machinelearning product project unstructured