Your father is definitely having CKD , chronic kidney disease
, most likely due to long standing hypertension
level of 3.4 however is not very alarming and you can wait till uour appointment with the nephtologist.
Try to keep his blood pressure under control, less than 140/90, by regular medicines, don't let him get dehydrated but at the same time don't give excess water if he has swelling on feet or feels breathless.
once the nephrologist
sees him follow his advise to reduce or control disease progression.