Burn everything important onto some old CDs or DVDs, that should be good enough. Filecoin seems cool too, but you have to pay in filecoin.
M-DISC use a more stable media, and should last much longer, but are (much) more expensive and require more recent burners. There are dual-layer M-DISC with higher capacities, too.
I did a bunch of research on long-term data archival and wrote it up here: https://photostructure.com/faq/how-do-i-safely-store-files/