Most long term memories are stored in the hippocampus. Some scientists are already working on trying to upload memories but as far as I'm aware they have only got as far as doing it with mice and only on a basic level, like remembering that pushing two buttons get you a food reward. The problem with memories being so complex is that your brain categorizes different aspects of the memory and stores it in different parts of the brain. Take for example a walk in the park - the sounds, smell, sights, and temperature are all stored separately. When you are reminded of a memory because of one particular category like a certain smell, this is your brain rapidly trying to pull all of the different categories together to reform the full memory.
The current experiments being done include creating a sort of artificial hippocampus that can be placed inside the head of a mouse (or at some point in the future, a human) containing the electrical signals that make up that memory. This involves first extracting the memories or electrical brain signals which is difficult as you first have to identify which signals are a part of the memory, and then programming them into the artificial hippocampus. It is hoped that one day this will be done on a human level but the main problem at the minute is the complexity of the programming required and our lack of knowledge on how different people interpret different memories. Also with things such as walking or eating that we have been doing nearly all of our lives, the memory is no longer stored in the hippocampus but in other parts of the brain like the frontal lobe responsible for elements of movement or the temporal lobe which plays a part in balance.
I think it would be cool to upload memories though and maybe one day it will be a reality but it is not likely to be done in the same way as in the matrix at first because this involves processing information directly out of the spinal chord I think.
I hope this helps and I haven't just overcomplicated stuff
