What redeem script is used in bitcoin core wallet when generate the address? I'm trying to generate the address 38DGj87axzmQiZeAd1w1y5FEmuu5a7pfBa in my bitcoin core wallet with code.

First, I dump the private key from the address, then I calculate the address from the private key. As the address is start form m, which is of P2SH bitcoin address type. And the P2SH address is constructed as

base58-encode: [one-byte version][20-byte hash][4-byte checksum]


Here I don't know what the script used to calculate the [20-byte hash] in the bitcoin core wallet?
You can use the getaddressinfo RPC command in the latest version of bitcoin core to get the hex encoded script for that address. But note that because you were able to get a private key, I assume this is a P2SH wrapped segwit address, which means the script is just an OP_0 opcode followed by the hash160 of the public key corresponding to that private key.