How did you manage the transfer? You need to ensure that you copied not only the Wordpress files but also the Database. Once you transfer the files to the new host you need to ensure that the wordpress files can now see the database on the new server. Typically they have a different naming structure so Wordpress usually complains and tells you that.
There are some ways of pulling and entire backup off your previous host and doing a restore on the new one, but there are too many variations on this to be able to help with steps. If you still have access to the old server you could try asking the new host to pull everything across. If they both have cPanel installed (very common) then it is a pretty easy thing that many hosts offer to do for free. This migrates everything, email, databases and website files.