connecting display with only usb-c ports to macbook pro 2014 (no usb-c ports) I'm inspecting a 4K monitor that has USB-C port only. I'd like to connect it to macbook pro 2014, which doesn't have an USB-C type of port.

I found some adapters that can convert between ports, but I am sceptic whether signal can be upgraded from older usb-3 port to usb-c? Is there any data loss? 

Background:
As you might know, issues with external displays and Apple devices are quite common. For this particular model, Apple has an official site in where it explains that this particular monitor is not compatible with devices that are older than 2015.

I am curious, if this is just because port incompatibly and whether this can be solved by using adapters.
No, you cannot connect the monitor to an USB A port (i.e. for example the non-USB-C USB 3 port you mention).

The monitor uses the so called "Alternate Mode" part of the USB-C connector. Essentially it means that the USB-C cable in addition to USB carries a seperate signal - for example DisplayPort as in this case.

Older USB connectors and cables do not have support for "Alternate Mode" and thus no adapters can be made.