It is not 100% clear what you are asking for an opinion on here but it sounds like a bunch of adapters to convert a 6 pin to an 8 pin which is not viable. You would need to buy a new PSU (I would suggest 550W for a 1070ti and the fact you have a 525W in there now) along with the graphics card, however, you want to be very careful trying to modify a pre-built system like a dell as alot of the components can be proprietary and non started with other products. Check that the current PSU is a 12vATX like most of the aftermarket PSU's and that the case and motherboard will support at GTX1070
EDIT: Just checked the item, 2 x PCIe x16 slots means it should be fine to support the 1070 but couldn't find any information about the PSU itself so you may need to check it's specs from the sticker on the side of the PSU