bash look for number followed by extension code example

Example 1: find linux with extension

find /home/username/ -name "*.err"

Example 2: bash find files with extension

# syntax
find </path/to/dir> -name '.<extension>'

# example 
find /export/home/jacquesk -name '*.txt'

# This will search in folder-path (including subdirectories) 
# of "/export/home/jacquesk", and will show any files 
# that end in '.txt'