In fact, that's not your case.
You need to:
1 - make a DB backup from phpmyadmin (not the ACP, in any case), you don't need the old files' backup at all.
2 - into the new test location (a sub-domain or localhost or whatever), copy the old folders:
3 - copy all of the files/folders of a vanilla 3.0.14 onto this test location overwriting/merging when required.
4 - install the this vanilla 3.0.14 (like you install a vanilla board, the same) that contains now your images and attachments.
5 - import your old DB there into the newly created one. Be sure your DB backup contains the DROP TABLE IF EXISTS stuff.
6 - amend your new config.php file to be able to connect to the DB (see your old one)
7 - install the STK that gives you a new ACP stand-alone panel and do a perfect clean to vanilla 3.0.14
8 - test you new vanilla that will contain all of your images and attachs
9 - is it ok? next steps..
10 - unistall the STK
11 - delete all of your folders/files except for config.php, images/, files/ and store/
12 - take a new version of the latest 3.1.x (currently is 3.1.10)
13 - once decompressed, copy all of its content (overwriting/merging when required) except for the config.php
file, you need the new-old one to connect to the DB there
14 - run install/database_update.php
15 - optional but important
: have a look to the config.php file, the 3.1.x version is a bit different, the 3.2.x also differs from others.
You should be able now to get in touch with a vanilla 3.1.10 version, test it deeply before to upgrade to Rhea. Also because it is better to wait a little bit after it will be released and see how's the crowd's feedback.
I hope I didn't forget some step, I don't think so ...
if my memory still serves (?)