Here are my suggestions:
Step 1: Upgrade your db to 3.5.
Step 2: If upgrade is successful, simply copy the graph.db folder.
Step 3: Go to 4.3 or any higher version
Step 4: Paste the folder from Step 2 in data/databases folder of Step 3.
Step 5: Open the terminal (from Step 3) and run this:
bin/neo4j-admin copy --from-database=graph.db --to-database=graphdb --force
(select any name for to-database)
Step 6: Once step 5 is successful, then run in Terminal:
bin/neo4j-admin store-info data/databases/graphdb (replace graphdb with the correct name)
Result should show:Store format version: SF4.3.0
Store format introduced in: 4.3.0
Once all the above steps are completed, copy the graphdb folder from data/databases (as in Step 6).
Step 7: Paste the copied db folder in V5.5 or above data/databases folder.
Final Step: Open Terminal and run this: bin/neo4j-admin database copy graphdb graphdb5 --force
Final Check: In Terminal run this:bin/neo4j-admin database info graphdb5 (use the correct name)
Result should show you format version 5 info.
That's all!