If the block diagram fits in the space properly, then there is no need of any conversions.

It is always good to have the diagram as image form as it would be preferred during the editing. Furthermore, please read the journal requirements for the diagrams and images.

There is no need of conversion at the initial stage of submission of manuscript. Also read the guidelines for authors given

by the journal, although the editor will direct you to make the changes accordingly.

good question!

Thank you for information

I suggest you draw your block diagram in the MS Visio and move to MS Word.