how to locate a name-not-specified file in bash? [on hold]

I have a bash like this to easily upload a file to my server:

FILE=../"$1"/1.txt
scp 1.txt remoteserver #upload the file to a remote server.

The $1 is for input directory and I have a lot of directories. But the txt file in all those directories are not all named "1.txt". What I can confirm is that each directory only contains one txt file.

How do I locate that file in this situation?

Update:

I tried to type FILE=../"$1"/1.txt

but when I check the file with:

if [ -f "$FILE" ]

I notice it's getting a false even when the file exist.

I figured out that:

$FILE is ../test/1.txt

"$FILE" is ../test/*.txt

So do I have to remove the pair of "?