Shell Script to read the file content and replace string in specific files in subfolders

Shell Script to read the file content and replace string in specific files
in subfolders

Hello I am new to shell scripting.I have requirement, I have file
containing list of files names and I have to search file name "string"
with the file in the directory and if the string matches then repalce the
file with content of the file.
example file.txt conatins below 1-23_abc 1-23_cbh
if "_abc" = abc.log in /usr/tmp then replace abc.log by 1-23_bac.log.
Ihope my query or requirement is clear.