Using old hardware to record to a modern iPhone

I have a numark idec and an iPhone 6. What I am trying to do is to record the audio that is being sent to the idec from an external device via phono cable (dual) on an iPhone because the idec has a record to iPod function as shown in QuickStart manual for the idec.

Because the idec is so old, it only has the ability to record to old iPods. Once I have an adaptor for the old connection is there any way I can record this audio to my iPhone (ios12)?

Old ipods mean 30-pin connector. It had audio in on pin 5 and 6.

The modern lightning connector does not have audio in, so the idec may not be suitable, and you need an adapter that can. As the iPhone 6 supports the Lightning to USB-3 adapter https://www.apple.com/shop/product/MK0W2AM/A/lightning-to-usb-3-camera-adapter the easiest way if the iPhone 6 is fully updated is probably getting this and a quality USB recording device presenting itself as a standard USB device not requiring special drivers.

Then garageband or any other recording app should do what you want.