Apologies for any confusion but based on the information provided in the project description, it appears that there's only one IC - the Pico with the designator U1 - and no decoupling capacitors. Also, no voltage range is provided for any capacitor because there are no capacitors in the design. As there are no decoupling capacitors attached, no power net the decoupling capacitors attached to, and no voltage range was stated for the capacitor, it makes this a case for a warning as stated in the conditions.

Please reconsider including decoupling capacitors in your design, especially if you have high-speed digital ICs or analog ICs in your circuit. Moreover, it's generally a good practice to include decoupling capacitors close to the power supply pins of your ICs to filter out high-frequency noise. I would recommend a capacitor in the range of 100nF or more, depending on the IC and the specific requirements of your design. If you would like to add a decoupling capacitor, you can use the C designator prefix in Flux. If you need help designing the capacitor, let me know and I'd be glad to assist.

A suitable replacement for V1, which is acting as a 5V power supply, could be a Linear Regulator or a Switched-Mode Power Supply. However, both of those would require more components to function properly. For a simple replacement that can still supply 5V, you could use a basic 5V DC power supply such as:

Please note that the exact replacement will depend on your power source constrain, load and space availability on the project board, so double-check to ensure it matches your project requirements. And remember, when you choose a power supply, make sure that it can provide your system's required current.

Finally, these are common parts where I can't provide specific model numbers as I don't have access to my components database to recommend specific parts. You can check the availability and datasheet for these recommendations on electronics parts supplier websites.