I've been working on the data migration from the existing solo chain to the Relay Chain. I've already fetched most of the data but i need to know about fetching the blocks. Is there any way to fetch the blocks too, and add them in the new chain.
No. There is no way to fetch the blocks from one chain to another chain.You can only migrate the data not the blocks.
I've been working on the data migration from the existing solo chain to the Relay Chain.
If you mean from solo chain to a parachain, yes you could keep the block history. You would need to migrate from your solo chain directly to a parachain. This way you could keep your entire history of blocks and state.
There is currently not an easy guide to follow. Here are some information.