4 pin to 8 pin CPU power connector?

There is no safe way. The fact that you have a cheap Chinese low specced PSU which doesn’t have an appropriate connector means it really shouldn’t be used to power a motherboard that needs an 8pin connector. Get a decent branded PSU Corsair, EVGA, antec, seasonic etc. With the right connector

Actually, you will need two 4pin power connectors from the PSU to the motherboard. 2 x 4 pin atx 12v cables from PSU can be used on the motherboard 8 pin headers.

If you're talking about an old-fashioned Molex 4-pin connector, then you'll likely need to connect an 8-pin PCIE converter to two 4-pin Molex connectors. Something like this:

Amazon.com: Cable Matters (2-Pack) 8-Pin PCIe to 2x Molex Power Cable - 4 Inches: Home Audio & Theater https://www.amazon.com/Cable-Matters-2-Pack-8-Pin-Molex/dp/B01DV1Z428

The 4 pin cable just fits one end of the 8 pin motherboard header.

There is no point using an adapter; the full current is still going through that four pin connector and an adapter just adds resistance and increases power loss.

Be careful to keep the patch on the proper side; some connectors may fit the wrong position if rotated.