This guide will give you the steps necessary to change your server’s seed.
Note: In order to use the new seed, you will need to remove the old world folder, for it must be regenerated. Stop the server, make a backup of your world folder via FileZilla if you wish to keep it, then please follow the instructions for the Multicraft in the following guide and delete the world folder. (https://www.mymultihosting.com/billing/knowledgebase/3/FTP-File-Access.html/)
Step 1: Log into your Multicraft control panel and make sure the server is stopped.
Step 2: Click 'Files' on the left and then on 'Config Files'.
Step 3: Look for the 'Level Seed' option. You may enter your seed here.
Step 4: Save the changes and start the server. It will generate a new world with the new seed setting.