How often will you access the files, and how often do they change? Is the
goal to also make them available for viewing online?


Amazon's product for this sort of thing is Glacier:
https://aws.amazon.com/glacier/

It would be somewhat expensive:
$.004/gb/mo, so $4/tb/mo, x200 = $800/mo,
or $9600/yr.

Let's take the 5 year cost to consider another possibility.

In 5 years you'd pay $48,000. So, could you build your own for less?

If you intend to basically never access this data, just archive it, tape
drives are the typical solution. To feel certain about the data, you would
buy a tape drive, and 2 sets of 12tb tapes, and store everything twice - in
2 separate locations, so a flood or fire can't knock you out. A tape drive
is $2000-4000 and the tapes are about $200.
Total cost about $10,000. You will need to read the tapes back once a year
to verify you've not lost any data. If you have, buy a replacement tape and
write from the other, duplicate tape. Other than that your ongoing costs
are essentially $0.

If you intend to rarely access the data, Drobos are simpler and cheaper.
Drobos store up to 114tb per box full of hard drives, and again to be safe
you want 2 sets stored in separate locations so a flood or fire can't knock
you out. That's 4 Drobos - they run about $4000 each so you're buying 2
sets of 2, $16000:
https://www.bhphotovideo.com/c/product/999544-REG/drobo_dr_
b1200i_1a21_b1200i_12_bay_nas_sas.html?ap=y&c3api=1876%2C%
7Bcreative%7D%2C%7Bkeyword%7D&gclid=EAIaIQobChMIkMGDyOrL2QIVDITICh
2whANtEAkYASABEgJ4BPD_BwE

Then you need to fill them with drives. You can buy 12tb drives for about
$400:
http://www.provantage.com/seagate-st12000nm0007~
7SEG911Q.htm?source=googleps&gclid=EAIaIQobChMI8o_q_
erL2QIVjgOGCh2HGANHEAkYBSABEgKp-vD_BwE

You need 48 of them, that's $19,200 in drives.

It's likely one of these drives will fail sometime in 5 years, so you
should budget for another drive sometime in that timespan - although prices
will have fallen in a couple years when you go to replace it. Maybe
$200-300.

Total cost would be $36000.

Much higher than the tapes, but you'd have 2 live arrays of your data ready
to be accessed whenever in exchange for quadrupling the cost of the
tapes/saving yourself 25% on Amazon.

Finally, Amazon AWS has Non-Profit Pricing *if you store nothing there
first*. They use the drug dealer method so you have to act like you're just
considering them as an option, but also Microsoft and Google seem
attractive. Fill out the form and they'll call you and talk about how
they're a maybe. They'll often extend free storage for a year or 3:
https://aws.amazon.com/government-education/nonprofits/credit-program/
https://aws.amazon.com/government-education/nonprofits/