You should be looking for sales (trades between people) and if you're going to use the SCM you'll need to properly do out the calculations using the key prices at the time of the sales. Besides, with quickbuyers at 33+ this looks low.

As Vrakos said, you'll need to divide the SCM sale price by the price of keys and then round to the nearest key

Which will go something like this, from the last month

SCM - https://steamcommunity.com/market/listings/440/Unusual%20Taunt%3A%20The%20Schadenfreude%20Unusualifier

Aug 3rd £38.84 / £1.71 = 23 keys

Aug 4th £52.69 / £1.69 = 31 keys

Aug 6th £53.02 / £1.66 = 32 keys

Aug 9th £35.37, £46.11 / £1.65 = 21 keys, 28 keys

Aug 11th £49.56, £45.11 / £1.66 = 29 keys, 27 keys

Aug 12th £53.56 / £1.65 = 32 keys

Aug 13th £45.43 / £1.66 = 27 keys

Aug 14th £45.29 / £1.66 = 27 keys

Aug 15th £51.79 / £1.67 = 31 keys

Aug 16th £47.88, £46.12 / £1.66 = 29 keys, 28 keys

Aug 19th £45.77 / £1.65 = 28 keys

Aug 20th £47.33 / £1.65 = 29 keys

Aug 21st £46.98 / £1.64 = 29 keys

Aug 23rd £46.88 / £1.64 = 29 keys

Aug 24th £51.37, £47.55, £51.47, £51.81 / £1.64 = 31 keys, 29 keys, 31 keys, 32 keys

Aug 26th £54.48, £48.03 / £1.64 = 33 keys, 29 keys

Aug 27th £54.63 / £1.63 = 34 keys

Aug 28th £48.61, £48.08 / £1.64 = 30 keys, 29 keys

Aug 29th £41.77 / £1.63 = 26 keys

Aug 30th £48.17, £48.19 / £1.63 = 30 keys, 30 keys

Aug 31st £47.22 / £1.66 = 28 keys

Sites such as marketplace.tf are also useful for cash-based sales, super useful for items like these. Again divide the sales by the key price on that day on that site:

https://marketplace.tf/items/tf2/9258;5;uncraftable;td-463 - Last month $74 / $1.81 = 41 keys

Sales in order are:

21, 23, 26, 27, 27, 27, 28, 28, 28, 28, 29, 29, 29, 29, 29, 29, 29, 29, 30, 30, 30, 31, 31, 31, 31, 32, 32, 32, 33, 34 and 41

SCM buyers are ~29 keys. Despite the buyers on backpack.tf being 34 keys+ there's a huge surplus of sales here at 29

I would make this 29 - 34 keys, excluding 41 as we are excluding a lot of lower sales