If you have to find files that are smaller than a particular file size, you can use
find command to do the job.
First, go to your folder where to start the find and type:
$ find . -type f -size -5k
This outputs all the files that are smaller than 5k and are located under the current folder (and subfolders).
.is the starting folder, which is the current folder in this case
-type fmeans that we want to search only files, not directories or anything else
-sizemeans that we want to search by size of the file
-5kis the size
You can find by any file size threshold, as well. Here is a guide:
See also: Find Files Larger Than 1GB in Linux