Dell WD19 dock with MacBookPro A1502

Dell Product Support – Dell Dock WD19

I don't think that you can. That dock wants to get a video signal from a USB-C (DisplayPort) source – and that MBP does not have USB-C ports.

While there is a bi-directional Apple Thunderbolt 3-to-2 adapter, it only translates Thunderbolt protocol. I'm pretty sure that while the connectors might physically fit, it won't produce the signals that the dock needs.

You might have better luck getting a wall-powered Thunderbolt 3 or 4 dock, and connecting it to your MacBook Pro with the aid of the Apple Thunderbolt 3-to-2 adapter. The dock would need to be wall-powered, as that adapter is not able to transmit power either from the TB2 side to the TB3 side, or vice versa. Likewise, the MBP would need to be running off battery power, or off a separate power supply, as it wouldn't be able to get power from the dock.

You could attach an external monitor directly to the Mac, provided that it can attach via HDMI or Mini DisplayPort, and that it has a resolution of 3840 x 2160 pixels or less. (On the HDMI port, the refresh rate will be only 30 Hz at that resolution.)