How important is VS How it is important ?
Something tells me that all sentences are totally incorrect ..:

1. They do not know how important is to follow the procedure

2. They do not know how important to follow the procedure is

3. They do not know how it is important to follow the procedure

Question

How important is VS How it is important ?
Something tells me that all sentences are totally incorrect ..:

1. They do not know how important is to follow the procedure

2. They do not know how important to follow the procedure is

3. They do not know how it is important to follow the procedure

Answer

They do not know how important it is to follow the procedure. (written English)

They don't know how important it is to follow the procedure. (spoken English)

Answer

The last one is ok, but strange. I think you are right: none of them say what you want to say.