Unfortunately, you had to have migrated your character from the Xbox 360 to the Xbox One before the deadline. Only characters that were migrated to the Xbox One/Playstation 4 from the previous generation of consoles were eligible for Veterancy Import into Destiny 2. If you logged into Destiny 2 using the same platform ID you used to play Destiny 1 and did not see your characters waiting for you at the character select screen, then your characters were not imported. It is not possible to import them now. You can recreate them and continue as normal; you just won't have any of the cosmetic goodies that would have come with the Veterancy Import. Please note that none of your equipment, levels, or abilities would have carried over. Everything that was brought in was purely cosmetic.