@Julien3z,
I think we have already replied this:
https://wplms.io/support/forums/topic/registration-form-confirm-password/
Try the below code in wp-admin > Plugins > Editos > Select WPLMS Customizer Plugin > wplms-customizer.php
add_action('wplms_before_registration_form','show_my_confim_pwd');
function show_my_confim_pwd(){
echo '<label '.(empty($settings['password_meter1'])?:'for="signup_password1"').'>'.
('Confirm Password','vibe-shortcodes').'</label>'.'<input type="password" onkeyup="checkPass(); return false;" '.(empty($settings['password_meter'])?'':'id="signup_password1" class="form_field"').' name="signup_password1" placeholder="'.('Confirm Password','vibe-shortcodes').'" ><div id="error-nwl"></div>';
}