If a psu was capable of delivering power to a 6 or 6+2 pcie graphics card lead, it would be included.
Adapters are not a solution since the power delivery is simply not there.
If one were to use adapters the danger is not only a psu failure, but also damage to the motherboard and anything connected to it.
And, avoid replacing with a cheap psu.
A cheap PSU will be made of substandard components. It may not have all safety and overload protections.
The danger is if it fails under load, it can destroy anything it is connected to.
It will deliver advertised power only at room temperatures, not at higher temperatures found when installed in a case.
The wattage will be delivered on the 3 and 5v rails, not on the 12v rails where modern parts
like the CPU and Graphics cards need it. What power is delivered may fluctuate and cause instability;
issues that are hard to diagnose.
The fan will need to spin up higher to cool it, making it noisy.
A cheap PSU can become very expensive.
Do not buy one.
Your easiest way to assess quality is to look at the warranty. 5 years gives you a 50/50 chance of getting a decent unit.
7 years or more will usually buy good quality.
Yes, a quality psu will cost more, but a good one is a long term investment.