If you boot to cmd line
If you need to change the timeout after what raspberry blank(turn off) connected displays. You need modify the config file /boot/cmdline.txt and add parameter consoleblank=xxx (replace x with desired value) for example the cmdilne.txt shlould looks like:
console=serial0,115200 console=tty1 root=PARTUUID=2f963b1a-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles consoleblank=3600
If you boot to xdesktop
If you boot to desktop enviroment you need edit the autostart file /etc/xdg/lxsession/LXDE-pi/autostart <- if you are using the pi account to log to your desktop. You need to add/edit params
@xset s off <- here you can set time for example @xset s 300
@xset -dpms
@xset s noblank