Thank you, Scampi. Should it be their actual supplier/company not just a country? Some refuse on the grounds of confidentiality. Shall I consider it as a NC?
Scampi's advice is good in in any sensible and sane situation, but your query smells a bit of a request from a UK retailer? If that's the case, sanity may sadly not actually apply...
You could try issuing an NC, but what is it that the supplier is not in conformance with? Do you have a formal agreed standard for this, that they haven't met? If not, it's going to be difficult that they should worry about not conforming with a standard/clause/agreement that doesn't exist 
Personally I'd suggest starting back at the beginning. Ask you customer exactly what it is they are expecting to see from this exercise. Don't agree to their expectations, but advise that you'll review with your supply chain once you fully understand what the customer is expecting.
For UK purposes it's not uncommon for the initial "target" expectation to be that a document will be provided that details the name and address of every raw material supplier, transport company, storage company etc all the way back to the base agricultural growers for every component of the product.
In practice this may or may not be feasible - even if everyone has the requisite traceability, some supply chains are large enough that it's simply not commercially viable / practicable, if for example you're buying a material that uses a commodity crop that may be sourced from hundreds or even thousands of growers.
Once you have an understanding of what your customer is expecting, then you can start discussions with your suppliers. I'd strongly advise calling them / arranging a Zoom meeting or similar, before bombarding them with email requests. That way you can get a better understanding of what is realistically achievable, what limitations there are etc - many will happily share some of their knowledge of their supply chains, and your attempts to discuss this are likely to be received more positively than simply sending yet another UK-based request for excessive detail that is often impractical or unrealistic for actual supply chains in the real world.
Once you have a decent understanding from your supply chain, you can then pick up with your customer to have a discussion about what is feasible vs. what they expected. Sometimes they'll be obstinate about this, but if they are you still haven't lost anything. But IMEX they'll often be relatively receptive as you can show a good understanding and that helps them better understand their own supply chains, which is surely the actual purpose of the exercise.
Good luck!
