This blog post provides the overall approach to upgrade from Oracle 8i (specifically 18.104.22.168) to Oracle 12c R1 (specifically 22.214.171.124)
Is your current version 126.96.36.199 (8i R3) ?
If so, this is the approach. You have to perform two upgrades. The first one is called an intermediate upgrade.
We recommend you to use dbua tool (database upgrade assistant GUI tool) instead of export and import tools.
1) Oracle 188.8.131.52 (8i R3) to Oracle 10.2.0.5
Do you have access to Oracle support https://support.oracle.com ?
If so, request them to provide you Oracle 10.2.0.1 software (base edition) through a service request. Install this 10.2.0.1 base software - Then download 8202632 which is the patch number for patchset 10.2.0.5 and apply to the 10.2.0.1 installed folder to bring it up to 10.2.0.5
Now do a direct upgrade from Oracle 184.108.40.206 to 10.2.0.5
2) In a separate path, install Oracle 220.127.116.11
Then upgrade the 10.2.0.5 upgraded database to Oracle 18.104.22.168.