How to tie a new foundation pour to existing

I think these are referred to as dowels and they are detailed as rebar connecting the old foundation to the new. Just as you'd pin a footing to bedrock, the rebar would be inserted into the old foundation and the new walls would be poured around them. I don't know the vertical spacing but this was just done on my house and my neighbor's. Neither of them had a sealant applied but that doesn't mean it's a bad idea. Note that I am not a builder and I'm just telling you what I've seen.

Good luck.