Hello,
I am an experienced Moodle developer with over 7 years of experience. I have completed more than 50 moodle upgrade projects for my clients and you can see them in my profile.
Moodle 1.9 is a very old version and 3.4 is the latest. Upgrading 1.9 to 3.4 requires the site to be upgraded to many intermediate version. During the upgrade, the database needs to be converted to UTF-8 format.
Please message me to have a discussion and create an upgrade plan. I am glad to answer any questions you may have.
Malaka