Your top case fan is 120x38mm, either a 1.4amp Nidec / 1.5a Delta, Dell part# or dp/n 7T3N3, available Dell Sales & probably pricey new, you'll have to get a quote.

The Nidec & Delta fan will also have a model # on the rear label; you can remove it, run the model# (&/or dp/n) through google/bing or eBay to shop around with. In the end, Dellware has huge contracts with Nidec / Delta to use the same basic 120x38mm fans across all desktop applications the past 7years, so a simple eBay search of Alienware fan or Area-51 fan or Nidec 120mm fan should yield results on new / used Nidec / Deltas. These are 4pin pwm fans, therefore, any 120x38, 120x32 or 120x25mm 4pin pwm will fit on your case wall fan bracket & should have a length suitable to reach the fan power header. Some owners look into qwieter types, like pwm Noctua fans for instance

The Nidec / Delta fans tend to have standard / average cables, as opposed to short or long length cables; measure yours if you like before looking into another 7T3N3, though it is 'safe' to say whatever you buy will probably reach the power plug-in header ... probably

Here is related info + another fan vid in this link from a recent related post: a little cooler

[View:https://www.youtube.com/watch?v=pDzt7lkCJFM:550:0]

Thank you,

I ordered a Nidec fan from e-Bay.