This topic has been discussed hundreds of times before, a simple search on CSC will provide a lot of details, and all the documents you need to review, are available on cisco.com under the CUCM documentation. You need to make sure to review the RNs, the upgrade guide, and the new and changed docs to find all the requirements for the upgrade to be successful, along with all the changes that will be required in the VM.
cisco.com -> Support -> All Products
Then either:
a) use the decision tree to look for the product
b) click the "Select a Product" drop down, scroll for the product, or type in the name of the product
HTH
java
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