Merging many rasters with Python script within QGIS using GDAL?

I have many rasters that im trying to combine in order to produce contours. They are in the .bil format so I understand that i need to translate them using gdal first but none of my attempts have worked.

I have tried to used gdal_translate and gdal_merge with no success.

import os 
import sys
import gdal 
chdir C:UsersjeswaDesktopGAL
SDKShell.bat
chdir C:UsersjeswaDesktopTESTY
dir /s/b *.bil >listbil.txt
gdalbuildvrt -input_file_list listbil.txt testscript.vrt
#error does not like N34025raster but passes 44 and 45
gdal_translate -of GTiff C:UsersjeswaDesktopTESTYtestscript.vrt C:/Users/jeswa/Desktop/TESTY/VIRTUALTIFF.tif
#no such thing as gdal_translate apparently