Cannot find my uploaded Bedwars map in the void.

Well sir, you gotta do /flyspeed 10
if you have essentials then fly and keep searching for it until you find it
or you can do the following steps:
1. put the world in single worlds and join it
2. after you joined it leave and rejoin the world in single player worlds again
3. take the world out of single player worlds as the world will have a data of your place
4. upload the world to aternos ( make sure to make it zip file )
5. enjoy your world

HOWEVER: I really don't recommend this way, it's better if you do /flyspeed 10 in air and search for the map.

you gotta leave a player data of your user

and can i see the error of /flyspeed 10 ?

Also make sure you joined the world in single player then take the world out of the single player world and upload it to aternos, not downloading it from internet and putting it on aternos instantly

Ohhh you are using vanilla, okay so remove the world from your aternos server
take the world and drag it to your MINECRAFT GAME world's files
join the world so you create a player data of yourself
then save&leave the world
after this you quit minecraft
go back to files
search for the world's files, take it and upload it to aternos
like this you dont have to search for itad you recorded a player data in the world so then when you join the server with the same account you joined the world in single player, you gonna be in the same spot that you last left in the single player world